USA: Solar Water Heaters Survive Energy Star Revisions
 USA: Solar Water Heaters Survive Energy Star Revisions

USA: Solar Water Heaters Survive Energy Star Revisions

 Energy Star Logo During the revision of the Energy Star specifications, solar water heaters were in danger of losing the label because of their long financial payback times (see The third draft of the revised requirements, which was published on 19 March, has now put an end to the uncertainty: the EPA has included solar water heaters even in its most recent document. A relief for all solar thermal producers – albeit they still criticise the high solar share required.

Solar companies had feared that the loss of the Energy Star would have affected the reputation of solar water heaters. With the new draft, they can now breathe a sigh of relief.

“EPA agrees that labelling solar water heaters has a positive impact on consumers and the environment, and has decided to retain the solar water heater category within this Energy Star Version 2.0 specification,” the Environmental Protection Agency writes as part of a comment included in the draft. It continues: “As with all products, EPA will continue to monitor the role that Energy Star plays in utility incentive programmes, and the ultimate impact that the programme has on market adoption.”

In the current draft, the EPA has changed the method with which to measure a system’s efficiency. To receive an Energy Star label, the former draft version required a certain Solar Fraction (SF). Now, the relevant criterion is the so-called Solar Energy Factor (SEF), which is part of the OG-300 certification. It represents the energy delivered by the total system, averaged across climates and divided by the electrical or gas energy put into the system. The SEF is calculated by dividing the efficiency of the auxiliary tank by the solar fraction.

To receive the Energy Star label, an electric back-up requires an SEF of 1.8, whereas a gas back-up must have an SEF of at least 1.2. This equals a solar fraction of 0.5, as the electric water heater has a minimum efficiency of 0.9 and the gas water heater one of 0.6, according to federal standards.

Heat pumps as a back-up would be subject to the same requirements as any electric water heater. But, solar systems combined with any other back-up systems, such as oil boilers or wood pellet burners, will not receive an Energy Star label. “Whole-home unit” means that the solar unit is intended to supply hot water to an entire home, not only to one or two taps.

Barry L. Butler, CEO of Butler Sun Solutions Inc, thinks the requirements are set too high. He writes in his comment letter: “EPA is not doing solar hot water any favours,” and continues, “A gas, electric or tankless water heater that saves only 18% over energy-inefficient models is given an Energy Star rating. Why should the same not hold true for solar hot water?” He claims that, “any solar system that reduces energy consumption by 20% (SF=0.2) should be given an Energy Star rating”, resulting in a solar fraction of 1.12 for electric tanks and 0.75 for gas tanks.

The solar energy association SEIA has not submitted any public comments to EPA.

Les Nelson, Head of the Solar Heating and Cooling Program at the International Association of Plumbing and Mechanical Officials (IAPMO), did not express any concerns about the high solar fraction. He proposes only little changes in the definition of eligible products: All products which are certified with the applicable American National Standard for solar water heaters or comply with SRCC OG-300 should be eligible for the Energy Star label.

The comment period for stakeholders ended on 16 April. An updated draft is expected for May or early June, followed by another comment period, a draft final and a final. If all goes well, the process will be complete by summer’s end. The effective date of the new regulations has been postponed to 1 February 2013.

More information:
See all drafts and comments on


Eva Augsten

Eva Augsten is a German freelance journalist specialised in renewable energies.